This invention relates to an image data processing method and apparatus as well as an image processing system for displaying an image that has been divided into a plurality of partial images.
Owing to the widespread use of such devices as digital cameras and scanners in recent years, there is rapidly increasing opportunity to capture desired an image and store image data representing the image on a storage medium such as a hard disk. Further, as a result of the proliferation of communications networks such as the Internet, it has become common for image data being managed by a remote computer to be downloaded to and displayed by a user""s own computer via the communications network.
FIG. 17 illustrates an example of an image format commonly used to store such image data. An image file is divided into a header portion and an image data portion, as shown in FIG. 17. Information necessary when data is read from this image file and auxiliary information which describes the content of an image generally are stored in the header portion. In the example of FIG. 17, the information stored in the header portion is information such as an image format identifier indicating the image format, file size, number of pixels in the X direction indicating the width of the image, number of pixels in the Y direction indicating the height of the image, depth-direction size (number of bits) representing the number of tones (number of colors) of the image, whether or not the image has been compressed, resolution, address offset toward a storage location at which image data has been stored in a bitmap format, and information (size data) on the color palette being used.
The image data portion stores image data in a bitmap format. Typical examples of such an image format are Microsoft""s BMP format and Compuserve""s GIF format.
When the image data portion having such a format is read out and displayed using a program, the usual practice employed to display all of the image data in the image data portion is to read out the image data from the beginning of the image data portion and display the image data successively from the upper left of the screen in raster-scan order.
Thus, in the prior art, the order in which image data is read out of an image file and displayed is fixed. Consequently, even if the intention of a producer of image data is to have someone first display and view only a part of the image before viewing the whole image, a technique for achieving this is not available.
FIG. 18 illustrates an example in which an image is displayed upon being divided into a plurality of tiles. According to this method, the image of interest is divided into seven tiles in the vertical direction and seven tiles in the horizontal direction using a plurality of tiles each of which comprises 64xc3x9764 pixels. Thus, the image is constructed using a total of 49 tiles. The numerals assigned to the tiles in FIG. 18 indicate the tile numbers. The tiles are numbered consecutively, i.e., xe2x80x9c0xe2x80x9d, xe2x80x9c1xe2x80x9d, xe2x80x9c2xe2x80x9d xe2x80x9c3xe2x80x9d, . . . , starting from the upper left of the image. In this example, each tile is displayed together with a border in order to explicitly show that the image has been divided into tiles. Examples of formats for thus dividing an image into a plurality of tiles include FlashPix and TIFF, and the respective standards have widely disclosed.
When such an image is displayed in enlarged form, the method generally used in the prior art involves changing the size of the image in FIG. 18 and then successively displaying each of the tile images starting from the tile at the upper left of the image of FIG. 18. Such an example is depicted in FIG. 19. FIG. 19 illustrates a state in which the enlargement and display of the image of the personal computer contained in the image of FIG. 18 is currently in progress. Here each tile in FIG. 19 is displayed upon being enlarged to a size that corresponds to four of the tiles shown in FIG. 18. It should be noted that, in a manner similar to that of FIG. 18, the numerals appearing in the tiles of FIG. 19 indicate the numbers of the tiles into which the enlarged displayed image has been divided. An area shown at 190 is an area in which an image that has already undergone enlargement processing is displayed, while an area shown at 191 is one in which enlargement processing has not yet been completed. The display in this area 191 is similar to that shown in FIG. 18. It should be noted that the borders indicating the boundaries of the tiles in FIGS. 18 and 19 are shown for the sake of convenience in order to clarify the individual tiles; they are not actually displayed on the screen.
Thus, with the prior art, when an image that has been divided into tiles is displayed in enlarged form, as shown in FIG. 19, it is difficult to discern what part of the displayed image is the enlarged part. When image data supplied from a server or the like is being displayed upon being received via a communication line having a low data transmission speed, the above-mentioned problem arises particularly in a case where the server is instructed to enlarge the image, whereby the enlarged image is displayed upon being received from the server via the communication line.
Accordingly, an object of the present invention is to provide an image data processing method and apparatus as well as an image processing system in which when an image based upon image data is displayed and the image is composed of a plurality of partial images, the partial images can be displayed in a desired sequence.
Another object of the present invention is to provide an image data processing method and apparatus as well as an image processing system in which partial images of a certain image can be requested in a desired sequence via a network, the image data received in the requested sequence and displayed in this sequence.
Another object of the present invention is to provide an image data processing method and apparatus as well as an image processing system in which when a certain image is displayed in a form obtained by combining partial images, it is easy to discern how far display of the partial images has been completed.
A further object of the present invention is to provide an image data processing method and apparatus as well as an image processing system in which when a certain image is displayed as a collection of partial images, the sequence in which the partial images are displayed can be decided and it is easy to discern how far display of the partial images has been completed.
Yet another object of the present invention is to provide an image data processing method and apparatus as well as an image processing system in which partial images of a certain image can be requested in a desired sequence via a network, the image data can be received in the requested sequence and can be displayed in this sequence, and in which it is easy to discern how far display of the partial images has been completed.